Re: [TenTec] NEC, ground, grounds, and radials

[Steve Hunt <steve@karinya.net>]

I see a very significant difference between the "approximate" formula 
and the one mentioned by Jerry; the former predicts that you can't 
achieve Zo lower than 87 Ohms, whilst the latter demonstrates that to be 
false. That seems like a difference which is meaningful.
But what are the amateur applications where a move to FEA would be a 
meaningful improvement over Jerry's formula? I'm struggling to think of any.
73,
Steve G3TXQ

On 08/01/2011 15:09, Jack Mandelman wrote:
> Forget about the formulas!  None of the discussed formulas is sufficiently 
> accurate of the wide ranges of S/d discussed.  All are approximations that are 
> reasonably valid only over their limited domains.
>
> A much more practical engineering approach would be to apply a finite-element 
> analysis of LaPlace's equation using the boundary conditions appropriate to the 
> geometry of interest.  For these types of problems a 2-D quasi-static analysis 
> provides much better accuracy than any formulas presented.
>
> Jack K1VT